The present invention concerns a torque motor with an annular rotor and an annular stator, which comprises a stator frame with iron cores and electrical windings arranged thereon.
Besides conventional rotary motors, which have drive functions involving the use of intermediate drive elements, so-called direct drives, in which the drive forces that are produced are delivered to the driven parts without intermediate drive elements, are being used to an increasing extent in a wide variety of technical areas. So-called torque motors of the type specified above are also counted among these direct drives.
The company publication “Direct Drives & Systems” by the company ETEL S.A., Switzerland, version 1.1 (Jul. 1, 1999.), describes a torque motor that has a stationary stator frame and an annular rotor that runs inside the stator frame. The rotor consists of a rotor frame and permanent magnets mounted on it, which provide permanent excitation. The stator, which also has an annular design, has an iron core and an electrical winding arranged thereon. Cooling elements, which are connected to a water cooling system, are mounted on the outside of the stator ring. With a diameter of 2.5 m, this motor can produce torques of about 10,000 Nm. In addition to producing large forces, a torque motor of this type allows precise positioning, large accelerations, and speeds in a large range of variation. However, as with other electric motors, there is the problem that very large and heavy rotating parts must be manufactured, shipped and assembled, which has a significant impact on production costs. Since direct drives of this type are frequently used in expensive total installations, the reliability of the motor is another important criterion. One of the most important causes of failure is damage to the electrical winding of the motor, which can result, for example, in a short circuit between individual windings. In a case such as this, the entire motor must be disassembled to replace the electrical winding. The individual windings are usually enclosed in a casting compound that consists of synthetic resin, impregnating resin, or the like, so that only a total replacement of the entire electrical winding is possible. Due to the size of these direct drives, disassembly is expensive. Since the direct drive is an essential component of complex installations, the installation cannot be used during the entire repair time when such a failure occurs.
U.S. Pat. No. 4,315,171 describes a step motor, in which the stator is divided into individual segments. The objective to be achieved with this previously known motor is to use the material required for the production of the stacks of iron plates more effectively by segmentation of the stator in order to lower production costs without adversely affecting the output capacity of the motor. To achieve this objective, the circular stator is divided into several segments, whose iron cores then comprise only circular segments, whereby the production-related material waste is reduced. Individual segments are then combined into a stator, and all segments are installed in a single common housing. The electrical windings must be secured in the housing for permanent operability of the motor, which is usually accomplished by casting the coils in the housing.